First and foremost, this is not the forum to be asking about how to fix your internet.
Secondly, DNS is an ambiguous error that can happen for a plethora of reasons, so without more into it's hard to say what a definitive fix might be.
Try unplugging your router or modem for a minute and then plugging it back in. If that doesn't work, try resetting router settings, and if worse comes to worse, contact your ISP.
But again, this is the PLAYSTATION ALL STARS FORUM. Not the IT forum.